Numerical Prediction and Experimental Validation of the Low-temperature Oxidation Characteristics of Coal in a Large-scale Furnace in an Adiabatic Environment

Abstract

ABSTRACT It is of great significance to study the characteristics of low-temperature oxidation of coal in an adiabatic environment for the prediction and control of coal spontaneous combustion. Coal spontaneous combustion experimentation can better simulate the field conditions and reflect and test the actual process underlying the spontaneous combustion of coal. Numerical simulation methods can provide a systematic solution for research on the dynamic evolution process of coal spontaneous combustion. In this study, a large-scale coal spontaneous combustion test bench was employed to test the oxidation heating characteristics and gas generation laws of Huangling coal samples from 303–443 K, revealing the spatiotemporal evolution characteristics of the gas concentration and temperature fields. Based on the theory of computational fluid dynamics (CFD), a mathematical model of the spontaneous combustion of coal in the adiabatic state is therefore constructed. The evolution law and distribution characteristics of the temperature and gas concentration fields of coal in the experimental furnace are simulated by Fluent. The results indicate that the position of the highest coal temperature in the experimental furnace mainly changed along the central axis and gradually moved down toward the air inlet as the coal temperature continued to rise. Above the critical temperature (353 K), the high-temperature point mobility was high, and only one-tenth of the ignition period could be utilized to travel along with more than one-third of the original distance from the intake side. In the furnace, O2, CO, and CO2 were distributed in the upper and lower layers at different concentration values. The concentration of O2 gradually decreased from the inlet side along the gas flow direction, but the concentrations of CO and CO2 demonstrated the opposite behavior. When the temperature exceeded 120°C, the consumption of O2 and the production of CO and CO2 gases were mainly distributed in the furnace body below 0.65 m. The simulation results are in line satisfactorily with the experimental results. This study provides theoretical support for field index gas and three zone division. The development of the model can improve the existing theory of coal spontaneous combustion and find a more systematic and reasonable criterion for judging coal spontaneous combustion.